Thermodynamic Analysis of Alumina Refractory Corrosion by Sodium or Potassium Hydroxide in Glass Melting Furnaces

Abstract

In this paper the high-temperature corrosion of refractories by MOH(g) found in the combustion atmospheres of typical air- and oxygen-fired glass-melting furnaces is examined using thermodynamic equilibrium calculations. These hydroxide species are considered to be the primary reactive alkali species since their partial pressures are significantly larger than those of M(g), the next most abundant gas-phase alkali-containing species expected in typical furnace atmospheres. Thermochemical simulations show that corrosion of α-alumina by NaOH(g) at typical furnace of around 200 ppm under oxy/fuel-fired conditions is unlikely as long as the refractory temperature exceeds 1564 K. For KOH(g) at 200 ppm, the temperature of the refractory must exceed 1515 K to avoid corrosion. Under air-fired conditions, is considerably lower (40-80 ppm); at 50 ppm, corrosion is thermodynamically unfavorable at temperatures above 1504 K. For KOH(g) at furnace levels of ∼50 ppm, temperatures must be above 1458 K. The paper also presents a re-evaluation of the thermodynamic and phase equilibrium properties of the and binary systems to develop accurate and self-consistent thermodynamic data. The data for (β-alumina) and are particularly critical since these phases are likely products of the corrosion of alumina refractories by MOH vapors in glass melting furnaces. © 2002 The Electrochemical Society. All rights reserved.